JP5231153B2 - Method for placing a substrate, method for transporting a substrate, support system and lithographic projection apparatus - Google Patents

Description

[0001] The present invention relates to a method of placing a substrate on the surface of a substrate holder and a computer-readable medium comprising computer-executable code that, when loaded into a computer assembly, allows the computer assembly to control such method. About. The invention further provides a method for transporting a substrate from a first substrate holder to a second substrate holder by a transport unit based on available transport data, and further the computer assembly controls such a method when loaded into the computer assembly. It relates to a computer readable medium that makes it possible. The present invention further provides a support system for supporting a substrate, a lithographic apparatus comprising such a support system, a device manufacturing method using such a lithographic apparatus, and a computer assembly when loaded into a computer assembly. It relates to a computer-readable medium comprising computer-executable code that makes it possible to control the method.

A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such cases, a patterning device, alternatively referred to as a mask or reticle, can be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (eg comprising part of, one, or several dies) on a substrate (eg a silicon wafer). The pattern is usually transferred by imaging onto a layer of radiation sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. A conventional lithographic apparatus exposes each target portion by exposing the entire pattern to the target portion at once, and a so-called stepper, while scanning the pattern with a radiation beam in a predetermined direction (“scan” direction) A so-called scanner is provided that irradiates each target portion by synchronously scanning the substrate in parallel or anti-parallel to a predetermined direction (“scan” direction). It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0003] In device manufacturing using a lithographic apparatus, an important factor in yield, ie the percentage of correctly manufactured devices, is the accuracy with which layers are printed with respect to previously formed layers. This is known as overlay and the overlay error budget is often 10 nm or less. In order to achieve such accuracy, the substrate must be aligned with high accuracy to the mask pattern to be transferred.

[0004] To achieve good image resolution and layer overlay, the irradiated surface of the substrate is accurately positioned on the support surface, ie the substrate holder, and is as flat and stationary as possible on the substrate holder during exposure. And must be maintained. For this reason, the substrate holder generally comprises a plate containing a plurality of projections, also called burls or pimples. The substrate can be placed on such a substrate holder so that the back side of the substrate contacts a bar that is all in a well-defined plane. By connecting the opening in the substrate holder to the vacuum generating device, the back side of the substrate can be securely clamped against the burl. Use of the bar in this manner ensures that only a portion of the backside region is actually pressed against the solid surface, thus minimizing the distortion effect due to particulate contamination on the backside of the wafer. This is because such contamination is most likely in the open space between the bars, rather than being pressed against the top surface of the bars.
and

However, when the substrate is fixed to the substrate table as described above, the substrate will bend on the bar. As a result, the image exposed on the substrate will shift locally. After development, when the substrate is again positioned on the substrate table for the second exposure, the position is different with respect to the plurality of bars, so the local image shift during the second exposure is different from the first exposure. It will be different. As a result, overlay errors are introduced.
2nd 1st

[0006] With the continuing desire to always image smaller patterns to produce devices with higher component density, there was a strong demand to reduce overlay errors, which provided a bar This leads to a demand for improved placement of the substrate on the substrate table.

[0007] It is also useful to provide a substrate placement method, a substrate transport method and a transport system that have improved placement accuracy over those known so far. To that end, embodiments according to the present invention provide a method of placing a substrate on a surface of a substrate holder, wherein the surface is provided with a plurality of bars, the method obtains the positions of the plurality of bars, and the surface of the substrate holder The method includes determining substrate placement data that enables a substrate to be placed at a specific position with respect to the plurality of bar positions above, and placing the substrate at a specific position according to the substrate placement data.

[0008] In one embodiment, the present invention provides a computer-readable medium comprising computer-executable code that, when loaded into a computer assembly, allows the computer assembly to control the method.

[0009] In one embodiment, the present invention provides a method for transporting a substrate from a first substrate holder to a second substrate holder by a transport unit based on usable transport data, and the second substrate holder includes a plurality of second substrate holders. And a method of providing a substrate on a first substrate holder and transporting the substrate from a first substrate holder to a specific position on a plurality of bars on a second substrate holder according to transport data by a transport unit. Placing the substrate at the specific position of the second substrate holder, the placing being performed according to a method of placing the substrate on the surface of the substrate holder as described above. In one embodiment, the method includes obtaining a plurality of bar positions on the substrate holder.

[0010] In one embodiment, the present invention provides a computer-readable medium comprising computer-executable code that, when loaded into a computer assembly, allows the computer assembly to control the transport method.

[0011] Also, in one embodiment, the present invention provides a support system for supporting a substrate, the support system configured to hold the substrate, and a substrate holder comprising a surface provided with a plurality of burls; A substrate processing device for placing the substrate on the substrate holder according to the placement data; a measurement unit for performing measurements usable to determine the positions of the plurality of bars provided on the surface of the substrate holder; and for the positions of the plurality of bars And a processor for determining substrate placement data that allows the substrate to be placed on the surface of the substrate holder at a specific location.

[0012] In one embodiment, the present invention also provides an illumination system that provides a radiation beam, a support structure that supports a patterning device that serves to impart a pattern to a cross section of the radiation beam, and a substrate as described above. A lithographic apparatus is provided that includes a supporting system that supports and a projection system that exposes a patterned beam onto a substrate.

[0013] In one embodiment, the present invention provides a device manufacturing method comprising projecting a patterned beam of radiation onto a substrate using the lithographic projection apparatus.

[0014] Finally, in one embodiment, the present invention provides a computer-readable medium comprising computer-executable code that, when loaded into a computer assembly, enables the computer assembly to control the device manufacturing method. provide.

[0015] Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings. Corresponding reference characters indicate corresponding parts in the drawings.

[0030] Figure 1 schematically depicts a lithographic apparatus according to one embodiment of the invention. This device
An illumination system (illuminator) IL configured to condition a radiation beam B (eg UV radiation or EUV radiation);
A support structure (eg mask table) MT configured to support the patterning device (eg mask) MA and connected to a first positioner PM configured to accurately position the patterning device according to certain parameters; ,
A substrate holder, eg a substrate table (eg wafer), configured to hold a substrate (eg resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate according to certain parameters Table) WT,
A projection system (eg a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (eg comprising one or more dies) of the substrate W; including.

[0031] The illumination system may be of various types, such as refraction, reflection, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof, to induce, shape or control radiation. Of optical components.

[0032] The support structure supports, ie bears the weight of, the patterning device. The support structure holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The support structure can use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device. The support structure may be, for example, a frame or table that may be fixed or movable as required. The support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system. Any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device.”

[0033] As used herein, the term "patterning device" is broadly construed to refer to any device that can be used to provide a pattern in a cross section of a radiation beam to produce a pattern in a target portion of a substrate. Should. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase shift features or so-called assist features. In general, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit.

[0034] The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase shift, attenuated phase shift, and various hybrid mask types. One example of a programmable mirror array uses a matrix array of small mirrors that can be individually tilted to reflect the incoming radiation beam in a different direction. This tilted mirror provides a pattern in the radiation beam reflected by the mirror matrix.

[0035] As used herein, the term "projection system" refers to, for example, refractive optical systems, reflective optics, as appropriate to other factors such as the exposure radiation used or the use of immersion liquid or vacuum. It should be construed broadly to cover any type of projection system, including systems, catadioptric optical systems, magneto-optical systems, electromagnetic optical systems and electrostatic optical systems, or any combination thereof. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system”.

[0036] As illustrated here, the apparatus is of a transmissive type (eg, using a transmissive mask). Alternatively, the device may be of a reflective type (eg using a programmable mirror array of the type mentioned above or using a reflective mask).

 [0037] The lithographic apparatus may be of a type having two (dual stage) or more substrate tables (and / or two or more mask tables). In such “multi-stage” machines, additional tables can be used in parallel, and one or more other tables are used for exposure while a preliminary process is performed on one or more tables. Can do.

[0038] The lithographic apparatus may be of a type capable of covering at least a portion of the substrate with a liquid having a relatively high refractive index, such as water, to fill a space between the projection system and the substrate. it can. An immersion liquid may be used in other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be immersed in a liquid, but rather that there is a liquid between the projection system and the substrate during exposure. It just means.

[0039] Referring to FIG. 1, the illuminator IL receives a radiation beam from a radiation source SO. The radiation source and the lithographic apparatus may be separate components, for example when the radiation source is an excimer laser. In such a case, the radiation source is not considered to form part of the lithographic apparatus, and the radiation beam is emitted from the source SO to the illuminator IL with the aid of, for example, a beam delivery system BD equipped with a suitable guiding mirror and / or beam expander. Passed to. In other cases the source may be an integral part of the lithographic apparatus, for example when the source is a mercury lamp. The radiation source SO and the illuminator IL may be referred to as a radiation system together with a beam delivery system BD as required.

[0040] The illuminator IL may include an adjuster AD for adjusting the angular intensity distribution of the radiation beam. In general, at least the outer and / or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution at the pupil plane of the illuminator can be adjusted. Furthermore, the illuminator IL may comprise various other components such as an integrator IN and a capacitor CO. The illuminator can be used to adjust the radiation beam to obtain the desired uniformity and intensity distribution in its cross section.

[0041] The radiation beam B is incident on the patterning device (eg, mask MA), which is held on the support structure (eg, mask table MT), and is patterned by the patterning device. The radiation beam B passes through the mask MA and passes through a projection system PS that focuses the beam onto a target portion C of the substrate W. The second positioner PW and the position sensor IF (for example an interferometer device, linear encoder or capacitive sensor) can be used to move the substrate table WT precisely to position various target portions C, for example in the path of the radiation beam B. . Similarly, with respect to the path of the radiation beam B using a first positioner PM and another position sensor (not explicitly shown in FIG. 1), for example after mechanical retrieval from a mask library or during a scan. The mask MA can be accurately positioned. In general, the movement of the mask table MT can be realized using a long stroke module (coarse positioning) and a short stroke module (fine positioning) that form a part of the first positioner PM. Similarly, the movement of the substrate table WT can be realized using a long stroke module and a short stroke module that form part of the second positioner PW. In the case of a stepper (as opposed to a scanner) the mask table MT may be connected only to a short stroke actuator or fixed. Mask MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. The substrate alignment marks as shown occupy dedicated target positions, but may be placed in the space between target portions (these are called scribe lane alignment marks). Similarly, in situations where a plurality of dies are provided on the mask MA, mask alignment marks may be placed between the dies.

[0042] The depicted apparatus can be used in at least one of the following modes:

[0043] In step mode, the mask table MT and the substrate table WT remain essentially stationary, while the entire pattern imparted to the radiation beam is projected onto the target portion C at a time (ie, a single stationary exposure). The substrate table WT is then shifted in the X and / or Y direction so that another target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure.

[0044] 2. In scan mode, the mask table MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (ie, a single dynamic exposure). The speed and direction of the substrate table WT relative to the mask table MT is determined by the enlargement (reduction) rate and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width (in the non-scan direction) of the target portion in a single dynamic exposure, while the length of the scan operation reduces the height (in the scan direction) of the target portion. Decide.

[0045] 3. In another mode, the mask table MT is maintained essentially stationary while holding the programmable patterning device, and the substrate table WT is moved or scanned while the pattern imparted to the radiation beam is on the target portion C. Projected on. In this mode, a pulsed radiation source is generally used, and the programmable patterning device is updated as necessary with each movement of the substrate table WT or during successive radiation pulses during the scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above.

[0046] Combinations and / or variations on the above described modes of use or entirely different modes of use may also be employed.

[0047] Figures 2a to 2c schematically illustrate the placement of a substrate on a substrate holder, such as a substrate table WT as is known in the art. The substrate table WT is provided with a plurality of protrusions 1 also called pimples or burls. The expression bar is mainly used herein, but it should be understood that the two are interchangeable here. There is usually a so-called vacuum seal at the edge of the wafer. In a lithographic apparatus that uses EUV, there is usually an electrostatic clamp. Many embodiments of the invention are not limited to vacuum systems, but are applicable to electrostatic clamps.

[0048] As shown in FIG. 2a, the substrate W moves toward the substrate table WT until the substrate contacts a plurality of bars provided on the surface of the substrate table WT.

[0049] The substrate W now rests on the substrate table WT with its back side in contact with the plurality of burls 1 on the surface of the substrate table WT, which is schematically illustrated in Figure 2b.

At this stage, air is sucked out of the space between the plurality of bars by connecting the opening 3 of the substrate table WT to the vacuum generating device 5. Air suction is schematically illustrated by the arrows in FIG. 2c.

[0051] FIG. 2d schematically shows details of the substrate W arranged on the substrate table WT, ie what is shown within the dotted circle in FIG. 2c. Due to the vacuum between the substrate W and the substrate table WT and the uneven surface of the substrate table WT due to the plurality of burls 1, the substrate W is locally deformed. As a result, the image exposed on the substrate W is locally shifted with respect to the desired image. When the substrate is placed again on the substrate table WT for the second exposure after development, the local image shift during the second exposure is different from that during the first exposure because the positions relative to the plurality of burls 1 are different. become. As a result, overlay errors are introduced.

[0052] FIG. 3 schematically illustrates a transport system that can be used in embodiments of the present invention. The transport system shown in FIG. 3 is suitable for use in a lithographic projection apparatus. It is configured to transport a substrate based on transport data available for it. The transport system includes a first substrate holder 11, a second substrate holder 13, and a transport unit 15.

The first substrate holder 11 is configured to hold the substrate 12. In one embodiment, the first substrate holder 11 is rotatable about its center, ie, the center of the surface that can hold the substrate. Thus, the axis of rotation is substantially perpendicular to the aforementioned surface.

[0054] The second substrate holder 13 is also configured to hold the substrate 12 on its surface. A plurality of bars may be provided on the aforementioned surface of the second substrate holder 13. Multiple bar positions can be obtained. In one embodiment, obtaining a plurality of bar positions includes at least four bar positions. Position acquisition can include calibration, particularly relative position with respect to a fixed part, for example a part of a substrate table.

When the transport system is used in a lithographic projection apparatus, the second substrate holder 13 may correspond to the substrate table WT and the held substrate 12 may correspond to the substrate W. Furthermore, the first substrate holder 11 may correspond to a substrate table used for the pre-alignment unit.

The transport unit 15 is configured to transport the substrate 12 from the first substrate holder 11 to the second substrate holder 13. The conveyance is executed according to the conveyance data described above. In the embodiment schematically illustrated in FIG. 3, the transport unit 15 picks up two subunits, ie the substrate 12 from the first substrate holder 11 and moves the substrate 12 towards the second substrate holder 13. And the three or more extendable pins existing in the second substrate holder 13, so-called E pins 17. The position and operation of the E pin 17 can be controlled by an E pin actuator 19, such as a Lorentz motor, which can be controlled by local electronics. As a safety measure when a power supply abnormality occurs, the E pin 17 can be configured to fall to the lowest position by the natural force of gravity. Thereby, it can be ensured that the E pin 17 is not damaged. The transport unit 15 can be configured to control the movement of the substrate 12 held by the gripper unit 16 in cooperation with the operation of the E pin 17, schematically illustrated by arrows 51 and 52, respectively. . The transport unit 15 can control the operation of the gripper unit 16 in the direction toward the E pin 17, that is, the operation toward the left side in FIG. 3, so that the substrate 12 can be appropriately positioned above the E pin 17. The transport unit 15 can then control the E-pins extending upwards in FIG. 3 toward the substrate 12 until they contact the substrate 12. The transport unit 15 continues to detach the substrate 12 from the gripper unit 16 and then move away from the E pin 17 of the gripper unit 16 until the gripper unit 16 no longer blocks movement of the substrate 12 toward the second substrate holder 12. Controls the operation, for example, movement to the right in FIG. Finally, the transport unit 15 can control the contraction of the E pin 17 until the substrate 12 is placed on the second substrate holder 13.

[0057] The transport system further includes a measurement unit 23, for example, an imaging device such as a CCD camera or a measurement sensor. If the measurement unit 23 is an imaging device, the measurement unit 23 can be configured to acquire images of a plurality of bars on the surface of the second substrate holder 13. When the measurement unit 23 is a measurement sensor, the position of each bar of the plurality of bars on the second substrate holder 13 can be measured. Alternatively or additionally, the measurement unit 23 can be configured to measure the position of a mark provided on the substrate 12 or the position of a mark provided on the second substrate holder 13.

[0058] The transport system further includes a processor 25. In an embodiment of the present invention, the processor 25 is configured to calculate substrate placement data to enable placement of the substrate 12 at an optimal position relative to the plurality of bar positions on the second substrate holder 13. The In the transport system as shown in FIG. 3, the processor 25 is configured to transmit the above-described substrate placement data to the transport unit 15 so that the transport unit 15 can control the placement of the substrate according to the substrate placement data. Is done.

In one embodiment, the processor 25 is communicatively connected to the measurement unit 32. This then calculates the substrate placement data using the information received from the measurement unit 23. Further, the processor 25 can communicate with the memory 27. The information stored in the memory 27 can be used by the processor 25 to calculate the substrate placement data described above. Further details regarding the function of the processor 25 will be described with reference to FIGS. 4 to 6 and FIG.

The operation of the second substrate holder 13 can be controlled by the control unit 29, and the control unit is desirable or necessary in view of the operation of the substrate arrangement data of the second substrate holder 15. In some cases, it can be communicably connected to the processor 25 or the transport unit 15. The data stream of the processor 25 and the control unit 29 is schematically illustrated by the arrow 55 in FIG.

[0061] Although the processor 25, transport unit 15, and control unit 29 are illustrated as separate elements in FIG. 3, if the control unit 29 takes the form of a computer assembly, eg, as described with respect to FIG. 9, the processor It should be understood that 25 may be incorporated into one of the transport unit 15 and the control unit 29.

[0062] Positioning of the substrate table WT in the lithographic projection apparatus is usually performed by so-called long stroke stage modules and so-called short stroke stage modules indicated by reference numerals 31 and 33 in FIG. The positioning ability combining these two stage modules 31, 33 provides accurate and rapid positioning. The long stroke stage module 33 typically provides coarse positioning and operation of the short stroke stage module 31 in multiple directions, typically three directions. The short stroke stage module 31 typically provides accurate operation and positioning with 6 degrees of freedom of the substrate W placed thereon. The short stroke stage module 31 can be separated from the long stroke stage module 33 by an air bearing 35 and can be driven by one or more Lorentz motors (not shown).

[0063] The control unit 29 may include separate control modules to separately control the operation and positioning of the short stroke stage module 29 and the long stroke stage module 33. Alternatively, the same control unit 29 may be configured to control the operation and positioning of both the long stroke stage module 31 and the short stroke stage module 33, this situation being illustrated by arrows 56 and 57 in FIG. 3, respectively. Has been.

As schematically illustrated in FIG. 3, the second substrate holder 13 can include not only the short stroke stage module 31 but also an additional element 37. The additional element 37 may comprise a recessed area that is large enough to accommodate the substrate 12. The concave surface includes the plurality of bars described above, and may further include openings between the plurality of bars for the purpose of establishing a vacuum environment as described with reference to FIGS. In an immersion lithographic projection apparatus, the recess of the additional element 37 may also have the purpose of containing and controlling immersion fluid.

[0065] Furthermore, the second substrate holder 13 can be provided with one or more marks.

[0066] In an embodiment of a method for placing a substrate on a surface of a substrate holder provided with a plurality of bars on the surface, the method includes determining substrate placement data and placing the substrate according to the substrate placement data. Place the substrate at a specific position with respect to the position of the multiple bars on the surface of the substrate holder, that is, the positions of the multiple bars as a whole, and the positions and directions of the multiple bars relative to each other, according to the substrate placement data Can do. A particular position relates to an optimal position that can be determined for several different criteria.

[0067] First, the optimum position relates to the optimum position related to the overlay, that is, the position where the minimum overlay error is recognized as the optimum position. In other words, the first exposure of the substrate in the lithographic apparatus is a specific for a plurality of burls configured in a specific pattern on the surface of a substrate holder, for example a second substrate holder as schematically illustrated in FIG. Consider the situation being performed at the location. Then, if the same substrate holder is used for a second exposure in a subsequent lithographic apparatus, the optimum position of the substrate exactly matches the position where the substrate was during the first exposure. However, the situation may be different when using a different substrate holder, ie a third substrate holder, for example a different substrate holder of the same lithographic apparatus or a similar substrate holder of a different lithographic apparatus, for a second exposure in a subsequent lithographic apparatus. When the third substrate holder has a surface provided with a plurality of bars arranged in the same manner as the substrate holder used for the first exposure, such as the second substrate holder, the optimal position of the substrate is that the substrate has a plurality of It is a position that is positioned with respect to the bar in the same manner as in the first exposure. If the multiple bar configurations are different for each substrate holder, the more difficult calculations will work for the optimal positioning calculation for the best overlay results. For example, a calculation that takes into account the expectation of how the substrate will deform in a particular configuration of multiple bars for the time being.

[0068] Second, the optimal position may be related to deformation. As illustrated with respect to FIG. 2d, a vacuum is created in the space between the plurality of bars, so that the substrate is locally deformed, and as a result, when the substrate is exposed in the lithographic apparatus during such a situation. Local exposure errors occur. The optimal position relates to the position where the local deformation is minimal. In an embodiment, minimizing local deformation corresponds to determining a least square or 99.7% interval and selecting a position where the least square is the least or 99.7% is optimal, respectively. Alternatively, it means that the position with the smallest average local deformation is selected. In another embodiment, local deformation minimization means that the local deformation is minimized at the location where the most critical features should be patterned, and the local deformation at other locations on the substrate is less than average. Is to grow.

[0069] Finally, the optimum position can be determined in advance. That is, the substrate placement location is stored in the memory of a computer assembly in communication with one or more lithographic projection apparatus, also referred to as a “matched machine”. Each substrate processed by these matched machines must be placed in a pre-indexed position on the individual substrate holder. Next, in order to establish the above-described arrangement, the board arrangement data is determined.

[0070] Needless to say, since overlay and deformation are closely related, the optimal position may be related to both. Eventually, consider again the situation in which the substrate is exposed while it is placed on the surface of a specific substrate holder in the lithographic apparatus and provided with a plurality of bars composed of a specific pattern. . Next, during subsequent exposure while the substrate is placed on the surface of a different substrate holder in the lithographic apparatus and provided with a plurality of burls configured in the same pattern as before The optimal position of the substrate may be different for multiple bars compared to the first exposure. This is because the plurality of bars provided on the surface of the substrate holder used for the first exposure are shaped in comparison with the plurality of bars provided on the surface of the substrate holder used for the subsequent second exposure. And / or different sizes.

FIG. 4 schematically shows a flowchart of a method for placing a substrate on the surface of a substrate holder according to the first embodiment of the present invention. First, in action 61, an image of a plurality of bars on the surface of the substrate holder is acquired by the imaging device. When using the transport system schematically shown in FIG. 3, the second substrate holder 13 is provided with a plurality of bars, and the imaging device corresponds to the measurement unit 23.

[0072] Thereafter, in action 63, the position of the plurality of bars on the surface of the substrate holder is determined by processing the image. This process is executed by the processor. The processor corresponds to the processor 25 when using the transport system schematically illustrated in FIG. In an embodiment, image processing includes using a recognition technique on the putter.

[0073] Next, in action 65, the processor calculates substrate placement data for allowing the substrate to be placed at an optimum position for the determined plurality of bar positions.

[0074] Finally, in action 67, the board is placed at the optimum position described above according to the calculated board placement data.

FIG. 5 schematically shows a flowchart of a method for placing a substrate on the surface of a substrate holder according to a second embodiment of the present invention. In this embodiment, first, in action 71, the position of each bar among the plurality of bars provided on the surface of the substrate holder is measured by the measurement sensor. When using a transport system as schematically illustrated in FIG. 3, the measurement sensor corresponds to the measurement unit 23, and the substrate holder corresponds to the second substrate holder 13.

[0076] Thereafter, in action 73, the positions of the plurality of bars on the surface of the substrate holder are constructed by processing the measured positions of each bar. Construction by processing is executed by the processor. When using a transport system as schematically illustrated in FIG. 3, the processor corresponds to the processor 25.

Next, in action 75, the board placement data is calculated again so that the board can be placed at the optimum position for the plurality of constructed bars.

[0078] Finally, in action 77, the board is placed at the optimum position described above according to the calculated board placement data.

FIG. 6 schematically shows a flowchart of a method for placing a substrate on the surface of a substrate holder according to a third embodiment of the present invention. First, in action 81, a memory is provided. The memory comprises position data regarding the position of the plurality of bars on the surface of the substrate holder. The memory corresponds to the memory 27 when using a transport system as schematically illustrated in FIG.

In action 83, a substrate is provided. The substrate includes a plurality of marks.

Thereafter, in action 85, the substrate is placed at the first position on the surface of the substrate holder, and the position of each mark of the plurality of marks is measured to calculate a quality index. The quality index is a numerical value that represents the quality of a specific position, that is, a measure of overlay error or a measure of the average amount of deformation that occurs at a specific position. In FIG. 7a, a top view of a substrate holder 101 with a surface 103 provided with a plurality of burls 105 is schematically illustrated. In FIG. 7b, a top view of the substrates 107, 111 with a plurality of marks 109, 113 is schematically shown.

[0082] Next, in action 87, the substrate is shifted to a second position on the surface of the substrate holder. The position of each mark of the plurality of marks is measured at this second position, and a quality index is calculated. The shift, measurement and calculation are performed a predetermined number of times represented by action 89. Actions 85 and 87 that consider the predetermined number of actions 89 equal to zero are schematically illustrated in FIG. 7b. The substrates 107 and 111 in FIG. 7b are arranged at two different positions on the substrate holder 101 in FIG. 7a. At one position, for example, the first position, the periphery of the substrate 107 is represented by a solid line, and the substrate 111 whose periphery is a dotted line indicates a substrate at another position, for example, the second position. The plurality of marks 113 in the latter position are shown in an ambiguous manner as compared with the plurality of marks 109 on the substrate 107 in the “around solid line” position.

In subsequent action 91, substrate layout data is calculated. This is calculated by the processor. Based on the substrate placement data, the substrate can be placed at the optimum position for the plurality of bar positions. In the process of calculating the substrate placement data, the position of the substrate having the smallest overlay error in the calculated state is used.

Finally, in action 93, the board is placed at the optimum position described above according to the calculated board placement data.

[0085] FIG. 8 schematically illustrates a flowchart of a method for placing a substrate on a surface of a substrate holder according to a fourth embodiment of the present invention. First, in action 121, a memory is provided. The memory corresponds to the memory 27 when using a transport system as schematically illustrated in FIG. The memory is the position of at least three mark sections provided on the substrate holder, i.e. at least three marks, or one mark if all marks provide information about one direction, e.g. the X or Y direction. To provide information about the direction, eg X or Y direction, to the position of a plurality of bars on the surface of the substrate holder with respect to the position of the two marks, and for example in the case of each Y direction or X direction mentioned above , Related to a direction substantially perpendicular to it. The term mark section is not necessarily related to the section of the mark and may also relate to other elements that can serve as some kind of reference, for example a reference bar that is not in contact with the substrate or any kind of seal I want you to understand.

Referring to FIGS. 7a and 7b, three marks 117 are provided, and the three marks 117 have a known relationship with the plurality of burls 105 present on the substrate 103 of the substrate holder 101. FIG.

[0087] In a subsequent action 123, the positions of at least three mark sections provided on the substrate holder are measured. The measurement can be performed with any suitable measurement unit. When using a transport system as schematically illustrated in FIG. 3, the measuring unit corresponds to the measuring unit 23. Also in action 125, the positions of the plurality of bars relative to the positions of at least three mark sections on the individual substrate holders are read from the memory. Data regarding such relative positions of at least three mark sections is provided to the processor. The processor corresponds to the processor 25 when using a transport system as schematically illustrated in FIG. In addition, measurement data acquired by the measurement unit is also provided to the processor.

In subsequent action 127, substrate placement data is calculated by the processor. Based on the substrate placement data, the substrate can be placed at the optimum position for the plurality of bar positions. The calculations performed by the processor use the positions of at least three mark sections as measured and the positions of the plurality of bars relative to the positions of at least three mark sections as read.

[0089] Finally, in action 129, the substrate is placed in an optimal position according to the calculated substrate placement.

[0090] FIG. 9 schematically illustrates one embodiment of a computer assembly that can be used in embodiments of the present invention. Such a computer assembly 200 may be a dedicated computer in the form of a control unit such as, for example, the control unit 29. The computer assembly 200 can be configured to load a computer readable medium comprising computer executable code. This allows the computer assembly 200 to transfer the substrate from the first substrate holder to the second substrate holder based on the transfer data available to it by the transfer unit when the computer executable code on the computer readable medium is loaded. Embodiments of the above method can be performed. Additionally or alternatively, the computer assembly 200 thereby provides a device manufacturing method for patterning a target portion of a substrate according to an embodiment of a lithographic projection apparatus comprising such a transport system when loaded with a computer readable medium. It becomes possible to execute.

[0091] The computer assembly 200 includes a processor 201, eg, a processor 25 in communication with the control unit 29, and may further include a memory 205, eg, a memory 27 connected to the processor 25. A memory 205 connected to the processor 201 includes a plurality of memory components such as a hard disk 211, a read only memory (ROM) 212, an electrically erasable / writable read only memory (EEPROM) 213, and a random access memory (RAM) 214. It's okay. Not all of the memory components need to be present. In addition, it is not essential that the memory components are in close physical proximity to the processor 201 or to each other. It may be arranged remotely.

[0092] The processor 201 may be connected to some type of user interface, such as a keyboard 215 or a mouse 216. A touch screen, trackball, audio transducer or other interface known to those skilled in the art may also be used.

[0093] The processor 201 can be connected to a reading unit 217, which reads data in a computer-executable code format, for example, from a computer-readable medium such as a floppy disk 218 or a CDROM 219, and in some situations computer-readable. It is configured to store data on the medium. DVDs or other computer readable media known to those skilled in the art can also be used.

[0094] The processor 201 connects to a printer 220 that prints output data on paper, as well as a display 221, such as a monitor or LCD (liquid crystal display), or any other type of display known to those skilled in the art. Can do.

[0095] The processor 201 is connected to a communication network 222, such as a public switched telephone network (PSTN), a local area network (LAN), a wide area network, by a transmitter / receiver acting as an input / output (I / O) 223. (WAN) or the like. The processor 201 may be configured to communicate with other communication systems via the communication network 222. In one embodiment of the present invention, an external computer (not shown), such as an operator's personal computer, may log into the processor 201 via the communication network 222.

[0096] The processor 201 can be implemented as an independent system or as multiple processing units operating in parallel, each processing unit configured to execute a larger program subtask. The processing unit may be divided into one or more main processing units having several sub-processing units. Some processing units of the processor 201 may also be located remotely from other processing units and communicate via the communication network 222.

In another embodiment, the position of the bar is determined using actual height measurement data of the wafer W loaded on the substrate support 13. The lithographic apparatus according to FIG. 3 can perform height measurements using known techniques for wafers W loaded on a support. According to this embodiment, the height measurement is performed at at least one linear point on the wafer surface. Particularly for overlay measurements, it is preferred to use linear points, as will be further described below. In a further preferred embodiment, linear measurement points parallel to the X and / or Y direction of the lithographic apparatus are used. The X and Y directions are parallel to the long stroke 31 and short stroke 33 stage modules according to FIG. In another embodiment, an arcuate position is selected to measure height data. The arc is preferably parallel to the position of the bar. Since the bar is preferably positioned around the center, the arc preferably follows this circle.

[0098] FIG. 10 shows an example of the measurement data (x-axis) of several measurement points or marks and the relative height of the wafer at these markers. Here, X indicates a row-shaped mark along the x-axis.

[0099] Typically, the bars are evenly spaced within many parts of the wafer table design. These equally spaced bars result in a periodic signal of height data. In an embodiment of the present invention, the phase of a periodic signal can be acquired using a discrete Fourier transform. This phase can then be used to determine the position of the table. As a result of determining the position of the table, the position of the table can be calibrated during subsequent wafer loading.

[00100] FIG. 11 shows the results of the data according to FIG. 10 after Fourier transform. Much of the noise is eliminated, leaving a sharp peak, which is used to determine the phase of the signal. This phase is then used to determine the position of the burl and the position of the table.

[00101] In FIG. 11, a frequency maximum of 400 is detected, which corresponds to a frequency of about 2.5 mm bar.

[00102] In one embodiment, a calibration measurement of a wafer positioned on a wafer table is performed using a more flexible wafer. A preferred measurement combines a more flexible wafer table with a height measurement. As the flexibility of the wafer increases, the signal / noise ratio increases.

[00103] In a further embodiment, a periodic signal similar to FIG. 10 is determined by performing overlay measurements. In this embodiment, a wafer with several lines with (narrow) equally spaced markers is used. In this embodiment, a wafer is loaded on a substrate support and a marker on a single line in a first direction, preferably the X direction, is measured. Next, the wafer is reloaded by positioning in a state shifted in the first direction, preferably the X direction. This shift is preferably equal to half the distance between the bars as determined at the first position. Thereafter, the mark is measured again. The difference in position generates a periodic signal. The same measurement is performed for Y, but this time shifts in the Y direction.

[00104] In one embodiment, wafer bending is affected. Bending can be mitigated by reducing the clamping pressure. Such an operation can be used instead of repositioning during overlay measurement.

[00105] The overlay measurement has a periodic signal. In embodiments that use repositioning, the signal indicates periodic displacement. Simulating such first and second measurements, the individual data are illustrated in FIG. Line 300 is a simulated bend at the first position, and line 301 is a simulated bend with the wafer in the second position. In this example, the position shift is approximately equal to a bar distance of 0.3.

[00106] Using frequency analysis, such as discrete Fourier transform, it is possible to determine the frequency of the bar as well as the frequency of the bar of height data. Frequency analysis has a good signal / noise ratio. The position of the bar can be obtained from the overlay signal 302, which is the difference between the data 300 and 301. The position of the bar can be obtained from the overlay signal 302 in several ways using the maximum and minimum values of the difference signal, possibly in the symbol and direction of the shift between the first position and the second position. Dependent.

[00107] Surprisingly, it has been found that the wafer bend between the bars is similar to a fourth order polynomial. Such a function uses a harmonic function, and in some cases can be described using a combination of harmonic functions. The Discrete Fourier Transform is a possible tool in determining the frequency of the main harmonic describing the bending of the wafer and additionally the position of the bar.

[00108] While this specification specifically refers to the use of lithographic apparatus in IC manufacturing, the lithographic apparatus described herein includes integrated optical systems, guidance and detection patterns for magnetic domain memories, flats It should be understood that there are other applications, such as the manufacture of panel displays, liquid crystal displays (LCDs), thin film magnetic heads, and the like. In the context of such alternative applications, the use of the terms “wafer” or “die” herein may be considered synonymous with the more general terms “substrate” or “target portion”, respectively, As will be appreciated by those skilled in the art. The substrate referred to herein can be processed before or after exposure, for example, in a track (generally a tool for providing a resist layer on the substrate and developing the exposed resist), metrology tool and / or inspection tool. Where appropriate, the disclosure herein may be applied to such and other substrate processing tools. In addition, the substrate can be processed multiple times, for example to produce a multi-layer IC, so the term substrate used herein may also refer to a substrate that already contains multiple processing layers.

[00109] The terms "radiation" and "beam" as used herein include ultraviolet (UV) radiation (eg, having a wavelength at or around 365 nm, 355 nm, 248 nm, 193 nm, 157 nm or 126 nm), Includes all types of electromagnetic radiation.

[00110] The term "lens" refers to any of various types of optical components, or combinations thereof, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components, where the context allows.

[00111] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, the present invention may be a computer program that includes one or more sequences of machine-readable instructions describing the methods disclosed above, or a data storage medium (eg, semiconductor memory, magnetic or optical disk) that stores such a computer program. ).

[00112] The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

[0016] Figure 1 depicts a lithographic apparatus according to one embodiment of the invention. [0017] Figures 2a-2c schematically illustrate the placement of a substrate on a substrate holder as known in the art. [0018] FIG. 2d schematically shows details of the substrate placed on the substrate holder as shown in FIG. 2c. [0019] FIG. 3 schematically illustrates a transport system that can be used in embodiments of the present invention. FIG. 4 schematically shows a flowchart of a method for placing a substrate on the surface of a substrate holder according to a first embodiment of the present invention. FIG. 5 schematically shows a flowchart of a method for placing a substrate on the surface of a substrate holder according to a second embodiment of the present invention. FIG. 6 schematically shows a flowchart of a method for placing a substrate on a surface of a substrate holder according to a third embodiment of the present invention. [0023] Figure 7a schematically shows a top view of a substrate holder comprising a surface provided with a plurality of bars. [0024] FIG. 7b is a top view schematically illustrating the substrate holder of FIG. 7a with the substrate disposed on top. FIG. 8 schematically shows a flowchart of a method for placing a substrate on a surface of a substrate holder according to a fourth embodiment of the present invention. [0026] FIG. 9 schematically illustrates an embodiment of a computer assembly that can be used in embodiments of the present invention. FIG. 10 schematically shows the height measurement data of the wafer positioned on the substrate table. FIG. 11 schematically shows a discrete Fourier transform of the data according to FIG. [0029] FIG. 12 illustrates the simulated overlay error of one embodiment for determining the position of the bar.

Claims (17)

A method of placing a substrate on a surface of a substrate holder, wherein the surface is provided with a plurality of bars, the method comprising:
By measuring the data that are related to the positions of the plurality of bars, and obtains the positions of the plurality of bars,
Based on the acquired positions of the plurality of bars, substrate placement data for allowing the substrate to be placed at a specific position with respect to the positions of the plurality of bars on the surface of the substrate holder is calculated. And
It looks including placing the substrate to the specific position according to the substrate placement data,
The method wherein the specific position is a position that results in a minimum overlay error as a result of placing the substrate . Obtaining the positions of the plurality of bars;
Obtaining an image of the plurality of bars on the surface of the substrate holder by an imaging device;
By processing the image comprises dividing by tying the positions of the plurality of bars located on the surface of the substrate holder,
Calculating the substrate placement data;
Based on the indexed position of the plurality of bars comprises calculating a substrate placement data for enabling placing the substrate in the specific position relative to the position of the plurality of bars, claim 1 The method described in 1. The method of claim 2 , wherein determining the positions of the plurality of bars by processing the image is performed using a pattern recognition technique. Obtaining the positions of the plurality of bars;
Measuring the position of each of the plurality of bars by a measurement sensor;
Constructing the positions of the plurality of bars on the surface of the substrate holder by processing the measured positions of each of the plurality of bars ;
Determining the board layout data;
Based on the constructed positions of the plurality of bars comprises calculating a substrate placement data for enabling placing the substrate in the specific position relative to the position of the plurality of bars, to claim 1 The method described. Determining the board layout data;
Providing a memory comprising position data relating to the positions of the plurality of bars;
Provide a substrate with a plurality of marks,
Placing the substrate at a first position on the surface of the substrate holder, measuring the position of each of the plurality of marks,
Shifting the substrate to a second position on the surface of the substrate holder, measuring the position of each of the plurality of marks,
Repeating the shift and measurement a predetermined number of times,
Calculate the overlay error for each measurement,
While using the position of the substrate having the minimum error calculated includes calculating a substrate placement data for enabling placing the substrate in the specific position relative to the position of the plurality of bars, according to claim 1 the method of. Determining the board layout data;
Providing a memory comprising position data relating to the position of the plurality of bars with respect to the position of at least three mark sections provided on the substrate holder;
Measuring the positions of the at least three mark sections provided on the substrate holder;
Reading the positions of the plurality of bars from the memory with respect to the positions of the at least three mark sections;
Calculating substrate placement data by using the measured positions of the at least three mark sections and the positions of the plurality of bars with respect to the read out at least three mark sections, wherein The method of claim 1 , comprising the calculating to allow placement of the substrate. A computer readable medium comprising computer executable code that, when loaded into a computer assembly, allows the computer assembly to control the placement method of any one of claims 1 to 6 . A method of transporting a substrate from a first substrate holder to a second substrate holder based on transport data available to it by a transport unit, the second substrate holder comprising a surface provided with a plurality of burls,
Providing the substrate on the first substrate holder;
Transporting the substrate from the first substrate holder in accordance with the transfer data by the transport unit to the specific position with respect to a plurality of bars on the second substrate holder,
Disposing the substrate at the specific position of the second substrate holder;
The method of performing said arrangement according to the method of arrange | positioning the board | substrate as described in any one of Claim 1 to 6 on the surface of a substrate holder. A computer-readable medium comprising computer-executable code that, when loaded into a computer assembly, enables control of the transport method of claim 8 by the computer assembly. A support system for supporting a substrate,
A substrate holder configured to hold the substrate and comprising a surface provided with a plurality of burls;
A substrate processing device for placing a substrate on the substrate holder according to substrate placement data;
By measuring the data that are related to the positions of the plurality of bars, the measurement unit to perform the available measurement to determine the positions of the plurality of bars provided on a surface of the substrate holder,
A processor for calculating the substrate placement data to allow the substrate to be placed on a surface of the substrate holder at a specific position relative to the positions of the plurality of bars based on the determined positions of the plurality of bars; , only including,
The support system , wherein the specific position is a position that results in a minimum overlay error as a result of placing the substrate . The measurement unit is an imaging device that acquires images of the plurality of bars on the surface of the substrate holder, and the processor further processes the positions of the plurality of bars to process the substrate arrangement data. The support system according to claim 10, which calculates. The support system of claim 11 , wherein a processor processes the image by using pattern recognition techniques. The measurement unit is a measurement sensor that measures the position of each of the plurality of bars; and the processor further constructs the positions of the plurality of bars by processing the measured positions of the plurality of bars. The support system of claim 10 , wherein the substrate placement data is calculated. The substrate holder is provided with at least three mark sections, the support system further comprising a memory communicatively connected to the processor, the memory comprising the plurality of burls relative to the position of the at least three mark sections. The support system according to claim 11 , comprising position data relating to position, wherein the measuring unit measures the position of the at least three mark sections. An illumination system providing a radiation beam;
A support structure that supports a patterning device that serves to impart a pattern to a cross-section of the radiation beam;
A support system for supporting a substrate according to any one of claims 10 to 14 ;
A lithographic apparatus, comprising: a projection system that exposes the patterned beam onto the substrate. 16. A device manufacturing method comprising projecting a patterned beam of radiation onto a substrate using the lithographic projection apparatus of claim 15 . 17. A computer readable medium comprising computer executable code that, when loaded into a computer assembly, enables control of the device manufacturing method of claim 16 by the computer assembly.